Such submerged surfaces are typically the underwater surfaces of a swimming pool, and automatic swimming pool cleaners are well known. Most automatic pool cleaners operate by interrupting the flow of water in a tube flowing through a hose to the pool filter pump. The flow is interrupted at a relatively high frequency in order to induce movement in the suction head of the pool cleaner by the abrupt cutting off of the flow of water being sucked up the tube and hose.
The suction head is thus moved over the surface of the pool to clean it. The mechanism used for interrupting the flow, varies from cleaner to cleaner, and it is this mechanism which can be crucial to the success of the cleaner. There must be a sufficient opening time, and size of opening, to allow debris such as leaves and the like to flow through, and the interruption must be of a sufficient frequency and speed to provide suitable movement.